209915437981 has 4 divisors (see below), whose sum is σ = 211075191964. Its totient is φ = 208755684000.

The previous prime is 209915437951. The next prime is 209915438021. The reversal of 209915437981 is 189734519902.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1828930756 + 208086507225 = 42766^2 + 456165^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-209915437981 is a prime.

It is a super-2 number, since 2×209915437981² (a number of 23 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (209915437951) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 579876720 + ... + 579877081.

It is an arithmetic number, because the mean of its divisors is an integer number (52768797991).

Almost surely, 2^209915437981 is an apocalyptic number.

It is an amenable number.

209915437981 is a deficient number, since it is larger than the sum of its proper divisors (1159753983).

209915437981 is a wasteful number, since it uses less digits than its factorization.

209915437981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1159753982.

The product of its (nonzero) digits is 4898880, while the sum is 58.

The spelling of 209915437981 in words is "two hundred nine billion, nine hundred fifteen million, four hundred thirty-seven thousand, nine hundred eighty-one".